Tuesday, October 25, 2005

More on form alignment

This article describes the various ways my forms are out of alignment. One of my problems is that although I marked a centerline on the strongback, the blocks of wood (cleats) used to hold the forms in place obscure the line. This is a problem since I used cleats on both sides of the form (thanks to the recomendation of Patrick C on the KBBB) to pinch the form in place, but didn't mark the centerline on the cleats (not sure how I could have since the cleats are put in place with the forms in position and thus the forms are in the way of effectively marking the line on the cleats - a catch 22). Also, my "elevation line" marking a horizontal straight line down the side of the strongback may not be 100% due to the fact that when I marked it using a string, the supports that hold the strongback were in the way of having the string run directly against the strongback. I used my combination square to press the string in against the strongback to mark the line, but who knows, it could be out by 1/16" of an inch in places.

Last night I was aligning forms and set up a stringline above the strongback and forms by tying some fishing line to the ends of a pair speed clamps clamped to the ends of the strongback, ensuring that the string was in line with the center-line marked on the strongback. The method I eventually settled on is to clamp a straightedge to the forms so that it is in line with the center-line marked on the form and that in essence extends that center line upwards so that it meets with the string line. I clamped a small level to the form such that it was paralell with one of the horizontal alingment lines on the form (waterline or sheerline). I then nudged the forms this way and that until 1) the ruler marking the center line just touched the string line, 2) the level was level, and 3) the mark indicating the center of the form hole was aligned with the "elevation line" (horizontal line marked on the side of the strongback). For some reason this is proving to be very difficult to achieve as when I nudge the form to get it to line up in one dimension, it shifts out of alignment in the other direction. Then, just when I had it perfect in 3 dimensions, I'd realise that somewhere along the way my ruler or level had shifted out of alignment.